This session is awesome IMHO!  So is it's follow on session - PLAT-776T.  I am a C++/Assembler developer and am just starting to get into HTML5, JavaScript, CSS, etc. let alone Contracts, Manifests, etc.  For someone like me who has no exposure to these technologies, I think Gabe did a superb job raising my awareness considerably on these technologies.  He has a upbeat presentation style as well which I found quite refreshing.